A High Reliability Asymptotic Approach for Packet Inter-Delivery Time Optimization in Cyber-Physical Systems

In cyber-physical systems such as automobiles, measurement data from sensor nodes should be delivered to other consumer nodes such as actuators in a regular fashion. But, in practical systems over unreliable media such as wireless, it is a significant challenge to guarantee small enough inter-delivery times for different clients with heterogeneous channel conditions and inter-delivery requirements. In this paper, we design scheduling policies aiming at satisfying the inter-delivery requirements of such clients. We formulate the problem as a risk-sensitive Markov Decision Process (MDP). Although the resulting problem involves an infinite state space, we first prove that there is an equivalent MDP involving only a finite number of states. Then we prove the existence of a stationary optimal policy and establish an algorithm to compute it in a finite number of steps. However, the bane of this and many similar problems is the resulting complexity, and, in an attempt to make fundamental progress, we further propose a new high reliability asymptotic approach. In essence, this approach considers the scenario when the channel failure probabilities for different clients are of the same order, and asymptotically approach zero. We thus proceed to determine the asymptotically optimal policy: in a two-client scenario, we show that the asymptotically optimal policy is a "modified least time-to-go" policy, which is intuitively appealing and easily implementable; in the general multi-client scenario, we are led to an SN policy, and we develop an algorithm of low computational complexity to obtain it. Simulation results show that the resulting policies perform well even in the pre-asymptotic regime with moderate failure probabilities

Effect of the symmetry energy on nuclear stopping and its relation to the production of light charged fragments

We present a complete systematics (excitation function, impact parameter, system size, isospin asymmetry, and equations of state dependences) of global stopping and fragment production for heavy-ion reactions in the energy range between 50 and 1000 MeV/nucleon in the presence of symmetry energy and an isospin-dependent cross section. It is observed that the degree of stopping depends weakly on the symmetry energy and strongly on the isospin-dependent cross section. However, the symmetry energy and isospin-dependent cross section has an effect of the order of more than 10% on the emission of light charged particles (LCP's). It means that nuclear stopping and LCP's can be used as a tool to get the information of an isospin-dependent cross section. Interestingly, the LCP's emission in the presence of symmetry energy is found to be highly correlated with the global stopping.Comment: 16 pages, 8 figure

The modern technology of iron and steel production and possible ways of their development

В изменяющейся мировой обстановке на рынке сырых материалов для черной металлургии разрабатывается ряд новых технологий по производству чугуна и стали, альтернативных существующим технологиям, которые способны обеспечить экономически устойчивую работу металлургических компаний. В дополнении к этому фокусируется внимание на экономии энергии и снижении выбросов парниковых газов в целях решения важнейших вопросов охраны окружающей среды. Изменение состояния окружающей среды ставит новые проблемы перед металлургической промышленностью, потребляющей значительные энергетические и топливные ресурсы. Отрасль вынуждена сосредоточить свое внимание на сокращении всех видов энергии, что приведет и к снижению выброса парниковых газов. Разработка альтернативных технологических процессов производства чугуна и стали способна обеспечить металлургическим компаниям экономически выгодную и устойчивую работу в производстве стали. Для оценки воздействий деятельности металлургических компаний на окружающую среду Инженерно-консалтинговой компанией ХАТЧ (НАТСH, Сanada) были разработаны новые методики моделирования, позволяющие квалифицированно и качественно оценивать риски в потреблении энергии и выбросах СО2 в металлургической промышленности. Методика для анализа выбросов углеродсодержащих парниковых газов названа G-CAP ™ (Зеленый Дом — Борьба с загрязнением воздуха углекислым газом), а для анализа энергоэффективности — En-MAPTM (Планирование действий при управлении энергией). Оценка существующего положения в большинстве интегрированных заводов показала, что они располагают возможностями по экономии энергии и борьбы с загрязнением атмосферы парниковыми газами, лучшие из этих заводов исчерпали эти возможности даже при высоких ценах на квоты выбросов СО2. В этом контексте важно оценить те важные особенности альтернативных технологий получения чугуна и стали, которые разработаны к настоящему времени. Эта статья содержит сравнительную оценку энергоэффективности и выбросов ПГ для некоторых выбранных альтернативных технологий производства чугуна и стали, которые рассматриваются для их реализации. Для этого применены методики G-CAP ™ и G-CAP ™ , элементы которых были разработаны в компании HATCH с основной целью количественной и квалификационной оценки потенциала экономии энергии и сокращения выбросов СО2 в металлургической промышленностиIn the changing global market scenario for raw materials for the steel industry, a number of novel iron and steelmaking process technologies are being developed to provide the steel companies with economically-sustainable alternatives for iron and steel-making. In addition, the steel industry is also focusing on reduction of energy consumption as well as green-house gas (GHG) emissions to address the crucial subject of climate change. Climate change is presenting new risks to the highly energy and carbon-intensive, iron and steel industry. The industry needs to focus on reduction of energy consumption as GHG emissions to address climate change. Development of alternate iron and steelmaking process technologies can provide steel companies with economically-sustainable alternatives for steel production. For managing climate change risks, novel modelling tools have been developed by Hatch to quantify and qualify potential energy savings and CO2 abatement within the iron and steel industry. The tool developed for abatement of greenhouse gas carbon is called G-CAPTM (Green-House Gas Carbon Abatement Process) while that developed for improving energy efficiency is called En-MAPTM (Energy Management Action Planning). Evaluation of existing operations have shown that most integrated plants have GHG and energy abatement opportunities; on the other hand, the best-in-class plants may not have a lot of low-risk abatement opportunities left, even at high CO2 price. In this context, it is important to assess these critical issues for the alternate iron and steelmaking technologies that have been developed. This paper presents a comparative evaluation of energy-efficiency and GHG emissions for some selected iron- and steelmaking technologies that are being considered for implementation. In this work, Hatch’s G-CAP™ and En-MAP™ tools that were developed with the main objective of quantifying and qualifying the potential energy savings and CO2 abatement within the iron and steel industry, were employed in the evaluation conducted

Electromagnetic induction and damping - quantitative experiments using PC interface

A bar magnet, attached to an oscillating system, passes through a coil periodically, generating a series of emf pulses. A novel method is described for the quantitative verification of Faraday's law which eliminates all errors associated with angular measurements, thereby revealing delicate features of the underlying mechanics. When electromagnetic damping is activated by short-circuiting the coil, a distinctly linear decay of oscillation amplitude is surprisingly observed. A quantitative analysis reveals an interesting interplay of the electromagnetic and mechanical time scales.Comment: 4 pages, to appear in Am. J. Phy

Direct and secondary nuclear excitation with x-ray free-electron lasers

The direct and secondary nuclear excitation produced by an x-ray free electron laser when interacting with a solid-state nuclear target is investigated theoretically. When driven at the resonance energy, the x-ray free electron laser can produce direct photoexcitation. However, the dominant process in that interaction is the photoelectric effect producing a cold and very dense plasma in which also secondary processes such as nuclear excitation by electron capture may occur. We develop a realistic theoretical model to quantify the temporal dynamics of the plasma and the magnitude of the secondary excitation therein. Numerical results show that depending on the nuclear transition energy and the temperature and charge states reached in the plasma, secondary nuclear excitation by electron capture may dominate the direct photoexcitation by several orders of magnitude, as it is the case for the 4.8 keV transition from the isomeric state of $^{93}$Mo, or it can be negligible, as it is the case for the 14.4 keV M\"ossbauer transition in $^{57}\mathrm{Fe}$. These findings are most relevant for future nuclear quantum optics experiments at x-ray free electron laser facilities.Comment: 17 pages, 7 figures; minor corrections made; accepted by Physics of Plasma

Groupwise Maximin Fair Allocation of Indivisible Goods

We study the problem of allocating indivisible goods among n agents in a fair manner. For this problem, maximin share (MMS) is a well-studied solution concept which provides a fairness threshold. Specifically, maximin share is defined as the minimum utility that an agent can guarantee for herself when asked to partition the set of goods into n bundles such that the remaining (n-1) agents pick their bundles adversarially. An allocation is deemed to be fair if every agent gets a bundle whose valuation is at least her maximin share. Even though maximin shares provide a natural benchmark for fairness, it has its own drawbacks and, in particular, it is not sufficient to rule out unsatisfactory allocations. Motivated by these considerations, in this work we define a stronger notion of fairness, called groupwise maximin share guarantee (GMMS). In GMMS, we require that the maximin share guarantee is achieved not just with respect to the grand bundle, but also among all the subgroups of agents. Hence, this solution concept strengthens MMS and provides an ex-post fairness guarantee. We show that in specific settings, GMMS allocations always exist. We also establish the existence of approximate GMMS allocations under additive valuations, and develop a polynomial-time algorithm to find such allocations. Moreover, we establish a scale of fairness wherein we show that GMMS implies approximate envy freeness. Finally, we empirically demonstrate the existence of GMMS allocations in a large set of randomly generated instances. For the same set of instances, we additionally show that our algorithm achieves an approximation factor better than the established, worst-case bound.Comment: 19 page